It can sometimes be useful to determine the proximity between wireless devices. A user of a given wireless device may wish to know what other wireless devices and/or their owners are nearby, for example. This may be useful in social settings, for example, where a user may want to be aware of other users in a crowded coffee shop, store, or public event. In another example, it may be useful to determine what wireless devices are inside or outside of a given perimeter, for security or accountability purposes.
The problem is currently being addressed in several ways. Some proposed solutions try to use Bluetooth or wi-fi received signal strength indication (RSSI) as a measure of distance between devices. This use of RSSI is highly inaccurate, however, due to the variations of this value as a consequence of environmental factors. The features of a building, such as metal or concrete structures, may lead to an unreliable solution. In addition, different manufacturers of wireless devices and routers may determine an RSSI in different ways, since there is no single agreed upon specification as to how to determine an RSSI, other than to bound them within the range of [−100,0]. A future Bluetooth standard may allow for proximity determination—such a standard may include a proximity profile. A standard like this may not be widely adopted for several years, however.
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